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MetadataUtils.java
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MetadataUtils.java
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/*
* Copyright 2014 The gRPC Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.grpc.stub;
import static com.google.common.base.Preconditions.checkNotNull;
import io.grpc.CallOptions;
import io.grpc.Channel;
import io.grpc.ClientCall;
import io.grpc.ClientInterceptor;
import io.grpc.ExperimentalApi;
import io.grpc.ForwardingClientCall.SimpleForwardingClientCall;
import io.grpc.ForwardingClientCallListener.SimpleForwardingClientCallListener;
import io.grpc.Metadata;
import io.grpc.MethodDescriptor;
import io.grpc.Status;
import java.util.concurrent.atomic.AtomicReference;
/**
* Utility functions for binding and receiving headers.
*/
public final class MetadataUtils {
// Prevent instantiation
private MetadataUtils() {}
/**
* Attaches a set of request headers to a stub.
*
* @param stub to bind the headers to.
* @param extraHeaders the headers to be passed by each call on the returned stub.
* @return an implementation of the stub with {@code extraHeaders} bound to each call.
* @deprecated Use {@code stub.withInterceptors(newAttachHeadersInterceptor(...))} instead.
*/
@ExperimentalApi("https://github.com/grpc/grpc-java/issues/1789")
@Deprecated
public static <T extends AbstractStub<T>> T attachHeaders(T stub, Metadata extraHeaders) {
return stub.withInterceptors(newAttachHeadersInterceptor(extraHeaders));
}
/**
* Returns a client interceptor that attaches a set of headers to requests.
*
* @param extraHeaders the headers to be passed by each call that is processed by the returned
* interceptor
*/
public static ClientInterceptor newAttachHeadersInterceptor(Metadata extraHeaders) {
return new HeaderAttachingClientInterceptor(extraHeaders);
}
private static final class HeaderAttachingClientInterceptor implements ClientInterceptor {
private final Metadata extraHeaders;
// Non private to avoid synthetic class
HeaderAttachingClientInterceptor(Metadata extraHeaders) {
this.extraHeaders = checkNotNull(extraHeaders, "extraHeaders");
}
@Override
public <ReqT, RespT> ClientCall<ReqT, RespT> interceptCall(
MethodDescriptor<ReqT, RespT> method, CallOptions callOptions, Channel next) {
return new HeaderAttachingClientCall<>(next.newCall(method, callOptions));
}
private final class HeaderAttachingClientCall<ReqT, RespT>
extends SimpleForwardingClientCall<ReqT, RespT> {
// Non private to avoid synthetic class
HeaderAttachingClientCall(ClientCall<ReqT, RespT> call) {
super(call);
}
@Override
public void start(Listener<RespT> responseListener, Metadata headers) {
headers.merge(extraHeaders);
super.start(responseListener, headers);
}
}
}
/**
* Captures the last received metadata for a stub. Useful for testing
*
* @param stub to capture for
* @param headersCapture to record the last received headers
* @param trailersCapture to record the last received trailers
* @return an implementation of the stub that allows to access the last received call's
* headers and trailers via {@code headersCapture} and {@code trailersCapture}.
* @deprecated Use {@code stub.withInterceptors(newCaptureMetadataInterceptor())} instead.
*/
@ExperimentalApi("https://github.com/grpc/grpc-java/issues/1789")
@Deprecated
public static <T extends AbstractStub<T>> T captureMetadata(
T stub,
AtomicReference<Metadata> headersCapture,
AtomicReference<Metadata> trailersCapture) {
return stub.withInterceptors(
newCaptureMetadataInterceptor(headersCapture, trailersCapture));
}
/**
* Captures the last received metadata on a channel. Useful for testing.
*
* @param headersCapture to record the last received headers
* @param trailersCapture to record the last received trailers
* @return an implementation of the channel with captures installed.
*/
public static ClientInterceptor newCaptureMetadataInterceptor(
AtomicReference<Metadata> headersCapture, AtomicReference<Metadata> trailersCapture) {
return new MetadataCapturingClientInterceptor(headersCapture, trailersCapture);
}
private static final class MetadataCapturingClientInterceptor implements ClientInterceptor {
final AtomicReference<Metadata> headersCapture;
final AtomicReference<Metadata> trailersCapture;
// Non private to avoid synthetic class
MetadataCapturingClientInterceptor(
AtomicReference<Metadata> headersCapture, AtomicReference<Metadata> trailersCapture) {
this.headersCapture = checkNotNull(headersCapture, "headersCapture");
this.trailersCapture = checkNotNull(trailersCapture, "trailersCapture");
}
@Override
public <ReqT, RespT> ClientCall<ReqT, RespT> interceptCall(
MethodDescriptor<ReqT, RespT> method, CallOptions callOptions, Channel next) {
return new MetadataCapturingClientCall<>(next.newCall(method, callOptions));
}
private final class MetadataCapturingClientCall<ReqT, RespT>
extends SimpleForwardingClientCall<ReqT, RespT> {
// Non private to avoid synthetic class
MetadataCapturingClientCall(ClientCall<ReqT, RespT> call) {
super(call);
}
@Override
public void start(ClientCall.Listener<RespT> responseListener, Metadata headers) {
headersCapture.set(null);
trailersCapture.set(null);
super.start(new MetadataCapturingClientCallListener(responseListener), headers);
}
private final class MetadataCapturingClientCallListener
extends SimpleForwardingClientCallListener<RespT> {
MetadataCapturingClientCallListener(ClientCall.Listener<RespT> responseListener) {
super(responseListener);
}
@Override
public void onHeaders(Metadata headers) {
headersCapture.set(headers);
super.onHeaders(headers);
}
@Override
public void onClose(Status status, Metadata trailers) {
trailersCapture.set(trailers);
super.onClose(status, trailers);
}
}
}
}
}